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WAEC Further Mathematics Past Questions & Answers - Page 45

221.

Simplify 8n×22n÷43n

A.

2n

B.

21n

C.

2n

D.

2n+1

Correct answer is A

8n×22n÷43n=23n×22n÷26n

22n+3n6n

= 2n

222.

Which of the following is a singular matrix?

A.

(1001)

B.

(2132)

C.

(38516)

D.

(0110)

Correct answer is A

No explanation has been provided for this answer.

223.

Simplify nP4nC4

A.

24

B.

18

C.

12

D.

6

Correct answer is A

nP4=n!(n4)!

nC4=n!(n4)!4!

nP4nC4=n!(n4)!÷n!(n4)!4!

= 4!=24

224.

A committee of 4 is to be selected from a group of 5 men and 3 women. In how many ways can this be done if the chairman of the committee must be a man?

A.

15

B.

40

C.

70

D.

175

Correct answer is D

From the five(5) men viable for the position of the chairman, one of them must be selected.

This implies; 4 men and 3 women are open for committee membership.  

7 C3 = 7!3!(73)!

76543213.2.1×4.3.2.1

= 35 × 5 = 175

225.

The mean age of n men in a club is 50 years. Two men aged 55 and 63 years left the club, and the mean age reduced by 1 year. Find the value of n.

A.

30

B.

20

C.

18

D.

14

Correct answer is B

Let the sum of the men's ages be f, so that

fn=50....(1)

Also, f(55+63)n2=501=49....(2)

From (1), f=50n

From (2), f118=49(n2)=49n98

f=49n98+118=49n+20

50n - 49n = n = 20